The Decomposition of Tryptophan in Acid Solutions : Specific Effect of Hydrochloric Acid

Abstract

The stability of tryptophan in aqueous solutions of HCl, H₂SO₄, or CH₃SO₃H under aerobic conditions was examined, and a specific effect of HCl was found. A kinetic study of the HCl-induced decomposition, tests for the free chlorine formation on heating the HCl used for the above run, etc. suggested that free chlorine produced by the air oxidation of HCl may hace participated in the decomposition of tryptophan. Thin-layer and ion-exchange chromatography of the decomposition products of tryptophan revealed that oxindolylalanine and dioxindolylalanine were formed by the reaction. These two compounds were also formed by treating tryptophan with ClO^- or N-chlorosuccinimide in a solution of HCl. These results support the above possibility.